Are there any known problems with the 98 Chevy Astro Van transmissions?

Answer 1

GM RWD mid-size and large Vans/SUV's (Jimmy, Bravada, TrailBlazer, Yukon, etc..) with an electronic 4sp automatic use the 4L60. The 4L60 has a known weakness with the Sun Gear Shell. It will take out 2nd, 4th and Reverse. This has been a known problem for years. It is not uncommom for the Sun Gear shell to crack at 70-80,000 miles. GM historically has not addressed this issue so if you use a GM part in the rebuild you may end up with the same issue. Do a google search on "sun gear shell" and "4L60" and you'll see what I mean. If replacing the part use an aftermarket part that has addressed this issue. If you have this fixed at the GM dealer they will charge you $800, will only replace the Sun Gear shell, and it will happen again. If you must have a dealer do it beg them it use an alternative part.

For those you have a stock sun gear shell in your 4L60 simply don't floor it from a dead stop and avoid full throttle 4-2 downshifts. I have 215,000 miles on the 4L60 in my '96 Astro Van and after learning of this issue several years ago I simply take it easy. The 4L60 in general is a good trans and is an electronic version of the 700-4R used in the mid 80's up thru 1993. Since they were also used in the Vette's and Camaro's the aftermarket has many parts to significantly beef-up these transmissions in high horsepower applications.

I had a problem on my 99. It wouldn't engage in reverse. Turns out there was a Gear Hub that fractured. I had to have it rebuilt.